Breast cancer is a heterogeneous disease with multiple etiologic and molecular pathways. To help elucidate the basis for this heterogeneity, the investigators propose (1) to describe the prevalence of over-expression of HER-2/neu and p53 in a large population-based study of breast cancer patients; (2) to relate known or hypothesized risk factors for breast cancer to the prevalence of over-expression of HER-2/neu and p53; (3) to assess whether over-expression of HER-2/neu or p53 is associated with differential survival; (4) to estimate the degree of association between race and the incidence of breast cancer with over-expression of HER-2/neu or p53; and (5) to distinguish particular patterns of molecular alterations which predict the incidence of second primary breast cancer. Specifically, they will retrieve 1,544 paraffin-embedded breast tissue blocks from women diagnosed with breast cancer between 1980 and 1982 who were part of a large population-based case-control study. Extensive risk factor and follow-up information have already been collected and computerized. Paraffin blocks will be analyzed for over-expression of the p53 tumor suppressor gene and HER- 2/neu oncogene using immunohistochemical staining techniques. The hypothesis is that the identification of pathologically unique subtypes of tumors will bear a stronger relationship with certain risk factors. The investigators state that the purpose of this study is to correlate epidemiologic risk factor information with specific molecular changes in order to differentiate these etiologic subgroups and to respond to the aims as briefly stated above.